1. Technical Field
The present invention relates to a refrigerant system applicable to a vending machine, a showcase or the like, and more specifically relates to a refrigerant system comprising a heat insulating housing provided with an accommodating space, and a refrigeration unit, attached to a lower portion of said heat insulating housing and in which a compressor, a gas cooler, an internal heat exchanger, a restriction means and an evaporator are disposed on a unit base.
2. Related Art
FIG. 8 is an explanatory cross-sectional view of one example of a conventional refrigerant system. The conventional refrigerant system 1A (an example of a showcase) comprises a heat insulating housing 3 provided with an accommodating space 2 inside, and a refrigeration unit 9 attached to a lower portion of the heat insulating housing 3, and in which a compressor 5, a gas cooler 6, a restriction means not shown are disposed on a unit base 4, and an evaporator 8 is accommodated in a heat insulating case 7 attached onto the unit base 4, and the compressor 5, the gas cooler 6, the restriction means not shown, and the evaporator 8 are sequentially connected to form a refrigeration circuit (see for example, Japanese Patent Laid-Open Publication No. H10-96532, No. 2003-56969 and No. 2003-65651). In FIG. 8, the reference numeral 17 denotes a fan for the gas cooler 6, the reference numeral 18 denotes a fan for the evaporator 8, the reference numeral 19 denotes a accommodating shelf for accommodating articles and the reference numeral 9A denotes an exhaust outlet.
When the refrigerant system 1A is operated, refrigerant gas compressed and discharged with the compressor 5 flows into the gas cooler 6. Then outside air is introduced by the fan 17 as shown by an arrow and is heat-dissipated by an air-cooling system. The heat-dissipated refrigerant passes through an internal heat exchanger not shown, and the refrigerant gas is heat-lost by a low-pressure side refrigerant to be further cooled. Then the cooled high-pressure side refrigerant gas reaches an expansion valve (restriction means) and the pressure is controlled to lower pressure so that the refrigerant gas has a two-phase mixture of gas/liquid. The mixture flows into the evaporator 8 as it is and the refrigerant is evaporated there to exhibit a cooling action by heat absorption from air. Then cooled air is introduced into the accommodating space 2 of the heat insulating housing 3 by the fan 18 as shown in an arrow (or in the opposite direction to the arrow) and is circulated.
After that the refrigerant flows out of the evaporator 8 and passes through an internal heat exchanger not shown to take heat from the high-pressure side refrigerant while receiving the heating action. Then the obtained refrigerant is perfectly gasified and the gasified refrigerant repeats cycles to be sucked into the compressor 5.
FIG. 9 is an explanatory cross-sectional view of another example of a conventional refrigerant system. The conventional refrigerant system 1E (an example of a showcase) comprises a heat insulating housing 3 provided with an accommodating space 2 inside, and a refrigeration unit 9, attached to a lower portion of the heat insulating housing 3, and in which a compressor 5, a gas cooler 6, a restriction means not shown are disposed on a unit base 4, a plurality of supporting columns 7B is fixedly provided on the unit base 4, a heat insulating case 7 is set on the column supports 7B and an evaporator 8 is accommodated in the heat insulating case 7, and the compressor 5, the gas cooler 6, the internal heat exchanger 10, the restriction means not shown, and the evaporator 8 are sequentially connected to form a refrigeration circuit (see for example, Japanese Patent Laid-Open Publication No. H10-96532, No. 2003-56969 and No. 2003-65651).
In FIG. 9, the reference numeral 17 denotes a fan for the gas cooler 6, the reference numeral 18 denotes a fan for the evaporator 8, the reference numeral 9A denotes an exhaust outlet and the reference numeral 19 denotes a accommodating shelf for accommodating articles.
When the refrigerant system 1E is operated, refrigerant gas compressed and discharged with the compressor 5 flows into the gas cooler 6. Then outside air is introduced by the fan 17 as shown by an arrow (or in the opposite direction to the arrow) and is heat-dissipated by an air-cooling system. The heat-dissipated refrigerant passes through an inner side tube of the internal heat exchanger 10 composed of a, double pipe and refrigerant gas heat exchanges there with a low pressure side refrigerant, which passes through an outer side tube of the internal heat exchanger 10 to be further cooled by being heat lost. Then the cooled high-pressure side refrigerant gas reaches an expansion valve (restriction means) and the pressure is controlled to lower pressure so that the refrigerant gas has a two-phase mixture of gas/liquid. The mixture flows into the evaporator 8 as it is and the refrigerant is evaporated there to exhibit a cooling action by heat absorption from air. Then cooled air is introduced into the accommodating space 2 of the heat insulating housing 3 by the fan 18 as shown in an arrow (or in the opposite direction to the arrow) and is circulated.
After that the refrigerant flows out of the evaporator 8 and passes through the outer side tube of the internal heat exchanger 10 to take heat from the high-pressure side refrigerant, which passes through the inner side tube of the internal heat exchanger 10 while receiving the heating action. Then the obtained refrigerant is perfectly gasified and the gasified refrigerant repeats cycles to be sucked into the compressor 5.
In the refrigeration cycle, fluorocarbon (R11, R12, R134a or the like) has been generally used as a refrigerant. However, when fluorocarbon is emitted into the atmosphere it has significant problems of the earth-warming effect, the ozone layer breakage and the like in large scale. Thus a study using other natural refrigerants having small influence on the environment, for example oxygen (O2), carbon dioxide (CO2), hydrocarbon (HC), ammonia (NH3), and water (H2O) as a refrigerant has been performed. Among these natural refrigerants, oxygen and water are low in pressure and it is difficult to use them as refrigerants in refrigeration cycles. Since ammonia and hydrocarbon are flammable, there is a problem that their handling is difficult. Thus a device using a transitional critical refrigerant cycles, to be operated on the high pressure side at super critical pressure, where carbon dioxide (CO2) is used as a refrigerant, has been developed (see Japanese Patent Laid-Open Publication No. H10-19401 and No. No. H07-18602).
However, in the conventional refrigerant system 1A, exhaust heat-exchanged by the gas cooler 6 moves in the direction of the heat insulating case 7, and after running against the heat insulating case 7 the exhaust moves around the heat insulating case 7 to flow toward the rear of the heat insulating case 7 so that it is discharged from the exhaust outlet 9A provided on a rear portion of the refrigeration unit 9 to the outside. Accordingly, airflow of the exhaust heat-exchanged by the gas cooler 6 is blocked by the heat insulating case 7 and airflow stagnates around the gas cooler 6 so that heat does not escape. Thus, air cooling of refrigerant gas in the gas cooler 6 becomes insufficient, resulting in an increase in the operation pressure. As a result the compressor 5 reaches an overload state and problems arise that an operation power is increased, a protection device is actuated to stop the compressor and the durability of the compressor 5 is adversely affected whereby its useful life of is shortened.
Alternatively, in the conventional refrigerant system 1E, exhaust heat-exchanged by the gas cooler 6 moves in the direction of the internal heat exchanger 10, and after running against the heat insulating case 7 and the internal heat exchanger 10, the exhaust moves around the heat insulating case 7 and internal heat exchanger 10 to flow toward the rear of the heat insulating case 7 and internal heat exchanger 10 so that it is discharged from the exhaust outlet 9A provided on a rear portion of the refrigeration unit 9 to the outside. As a result, airflow of the exhaust heat-exchanged by the gas cooler 6 is blocked by the heat insulating case 7 and the internal heat exchanger 10, and airflow stagnates around the gas cooler 6 so that heat does not escape. Thus, air cooling of refrigerant gas in the gas cooler 6 becomes insufficient, resulting in an increase in the operation pressure. As a result the compressor 5 reaches an overload state and problems arise that an operation power is increased, a protection device is actuated to stop the compressor and the durability of the compressor 5 is adversely affected whereby its useful life of is shortened. Further, since exhaust heat-exchanged by the gas cooler 6 flows around the internal heat exchanger 10, there are problems that the heat-exchanging efficiency of the internal heat exchanger 10 is lowered and condensation occurs on a surface of the outer side tube (the low pressure side refrigerant, which flows out of the evaporator 8, flows) of the internal heat exchanger 10.
Further, in a case where carbon dioxide is used as a refrigerant, the refrigerant pressure reaches about 150 kg/cm2 G on the high pressure side. On the other hand, in a refrigeration cycle using carbon dioxide as a refrigerant so that the refrigerant pressure reaches about 30 to 40 kg/cm2 G on the low pressure side, the refrigerant pressure becomes higher and the refrigerant temperature also becomes higher as compared with fluorocarbon. Particularly, when single-stage compressing compressor is used, portions, which adjoin between the high pressure side portion and the low pressure side portion are formed in the respective sliding members. Thus there is a problem that since the differential pressure easily generates sliding loss or leak loss and the refrigerant temperature is increased, the air cooling of the refrigerant gas in the gas cooler becomes more insufficient.